Re: multiple targets

[Luke Shumaker]

On Tue, 19 Jan 2016 04:56:42 -0500,
Phillip Lord wrote:
> While writing a make file, I've just hit the situation where I need to
> write a rule of the form:
> 
> 
> a b c d e: x y z
>     generate_abcde
> 
> 
> Unfortunately, this doesn't work as the semantics are equivalent to the
> rules where the targets are separate -- that is generate_abcde gets run
> multiple times.
> 
> I've done some poking around, and found that a couple of solutions,
> either with pattern rules or otherwise by creating an intermediate file,
> as described here:
> 
> http://lists.gnu.org/archive/html/help-make/2007-04/msg00021.html
> 
> My understanding is that there is no other way to do this, but I was
> wondering why this was the case; would it be possible to support to make
> for this directly?

Right now, no, there is no support for that in GNU Make.

The automake manual has a section on how to do multiple outputs (that
are all gross, because automake supports (nearly?) every
implementation of make):

  https://www.gnu.org/software/automake/manual/html_node/Multiple-Outputs.html

As noted in the mailing list thread you linked, if {a,b,c,d,e} and at
least one of {x,y,z} have a common stem, then pattern rules can be
used with GNU Make (this syntax is non-portable).  However, if the
filenames have nothing to do with eachother, then GNU Make has no way
of expressing that.

-- 
Happy hacking,
~ Luke Shumaker